NUCLEAR MOTIONS OF AN INCLUSION COMPLEX OF CALIX[4]ARENE

The 2:1 inclusion complex of p-tert-butylcalix[4]arene and p-xylene wa s investigated by a combination of inelastic neutron scattering, WS, e xperiments and MM3 molecular mechanics calculations. Since the INS spe ctrum depends only on the vibrational frequencies and the form of the normal modes, the reasonable agreement between experiments and calcula tions shows that they can be simulated by the MM3 model. Further it va lidates the use of MM3 to search for possible spectral signatures of a hypothetical 1:1 inclusion complex and for a partial study of the p-x ylene dynamics within the cage. The latter is accomplished by locating the transition state of a complicated motion of the guest molecule in side the cavity. Transition-state theory is used to calculate the temp erature-dependent rate constants, and subnanosecond time scales are ob tained.